Nitrogen oxides (NO.sub.x) are gaseous emissions from numerous industrial process, such as fossil fuel combustion, pulp and paper manufacturing, and pharmaceutical production. Upon release into the atmosphere, NO.sub.x compounds have demonstrated various deleterious effects including the production of acid rain and stratospheric ozone damage. Nitric oxide (NO) and nitrogen dioxide (NO.sub.2) are the two most common forms of NO.sub.x. Nitrous oxide (N.sub.2 O) , another form of NO.sub.x, is not as abundant from combustion sources but has a significant impact on the greenhouse effect, contributing to 5% of global warming due to its long residence time (&gt;150 years) in the atmosphere. N.sub.2 O has also been shown to increase in concentration from fluidized bed boilers as well as from NO.sub.x reburners.
NO.sub.x gases, from industrial sources, have the potential of being converted, via anaerobic bioprocessing, to diatomic nitrogen (N.sub.2), an environmentally benign compound. Bioprocessing of NO.sub.x compounds, using naturally occurring nitrate-reducing bacteria, have been demonstrated to effectively convert NO.sub.x to diatomic nitrogen (N.sub.2), with gas solubility being the limiting factor.
Perfluorocarbons are hydrocarbons with fluorine substituted for hydrogen. These chemicals allow for increased gas solubility, are chemically inert, and have not been demonstrated to be biodegradable or been shown to be toxic to microorganisms.
Perfluorocarbons have received little attention in industrial microbiology for anaerobic bioprocesses or hydrocarbon or volatile organic compounds degradation. This invention demonstrates the potential for the use of perfluorocarbon emulsions in the bioprocessing of industrially important gases, hydrocarbons and volatile organic compounds. Perfluorocarbons are colorless, dense, nontoxic liquids having very low surface energies and consist of a ring or straight chain hydrocarbon in which hydrogen atoms have been replaced by fluorine atoms. Examples are: perfluorodecalin, perfluorohexane, perfluoropentane, and perfluorobenzene.
Nitrous oxide (N.sub.2 O) was chosen as a model NO.sub.x compound, primarily because all NO.sub.x compounds entering a bioprocess must first be reduced to N.sub.2 O prior to reduction to N.sub.2. Perfluorocarbon emulsions were employed to increase N.sub.2 O transfer in anaerobic, aqueous growth media in order to facilitate gas transfer to pure cultures of bacteria.